Support arm



FIG. 1 is a perspective view of my support arm;

FIG. 2 is a front view of my support arm;

FIG. 3 is a first side view of my support arm;

FIG. 4 is a second side view of my support arm;

FIG. 5 is a top view of my support arm;

FIG. 6 is a bottom view of my support arm; and,

FIG. 7 is a rear view of my support arm.

The portions of the support arm shown in broken lines form no part of the claimed design. 

The ornamental design for a support arm, as shown and described. 